Science Questions

How are plants modified to be pest resistant?

Sat, 15th May 2010

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Sarah asked:

We know that some genetically modified foods are designed to be pest-resistant, and were wondering about the mechanism - how do they do it?


We put this question to Dr Jim Haseloff, from Cambridge University:

Jim - Organic farmers actually use bacteria Ė the Bacillus thuringiensis bacterium which has a protein which affects the gut of specific insects and that protein, of course, is encoded in the gene and that gene can be then transferred to plants using genetic engineering techniques.  So itís essentially a surgical procedure of isolating the particular gene using a natural bacterium to transfer that into a plant and then once itís in there, itís used as a gene thatís for breeding.

Chris -   So presumably, with synthetic biology, what one would do is to say "rather than take that toxin from a bacterium, what would be better would be to study the organisms that we want to make the plant resistant to, and then find our own way of making the plant resistant" and put some kind of specific thing into the plant that will be even better than what a bacterium toxin could do for us.

Jim -   Thatís certainly feasible in the longer term.  I think most of the emphasis at this point is on better engineering using existing systems, existing parts from what we know in the biological world and rearranging their delivery inside say, for example a crop system, where you might get around some of the issues weíre talked about earlier in the program where youíve got some insects which are immune to these very specific toxins and can escape.  So you can imagine a second element that would deal with that for example.


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Sarah asked the Naked Scientists: Hi there, We know that some genetically modified foods are designed to be pest-resistant, and were wondering about the mechanism. My husband thinks that they are engineered to produce a pesticide (ie. a toxin). I think that it's more likely that the crops are engineered to produce a compound that is unpalatable to whatever insects typically eat them. Can you settle this debate? Many thanks! Sarah (Canada) What do you think? Sarah, Tue, 11th May 2010

Hi there

yes you are right

In fact, engineers now can manipulate the genes of living organisms which can be transformed as  planned but the further effects of that are not always studied or well known

to give to a plant the capability to kill the insect, engineers have to do lots of work in the lab to isolate the gene producer of the toxin  and introduce it in the genome of the plant so the resulted plant  is genetically modified and hence it behaves as a pesticide

but the most important question here is "are we eating pesticides" ??

Myriam myriam, Thu, 13th May 2010

The genes to encode a pesticide ( or a protein that is like a pesticide to the particular target) is selected from a donor organism that produces it naturally. This is then placed in the recipient cell by various methods, either via a virus or by injection or by explosive recombination.

The surviving cells are then cultured and the descendants are tested to see who has the gene in the correct place more or less, and if the gene is expressed and is effective. The cell lines that pass are then grown in vitro, and the seedlings are planted and allowed to grow to maturity and produce seed. Most important ( from the perspective of the manufacturer) is to make sure the seed that the farmer gets is sterile, and does not produce a viable seed, whilst meeting most of the resistance requirements if feed with appropriate fertiliser and copious water. SeanB, Thu, 13th May 2010

Similarly some crops are 'engineered' to withstand temperature variations or extremes. By your logic we should be asking 'are we eating anti-freeze'. ricbritain, Sat, 15th May 2010

And to an extent Myriam would be right! Plants with increased cold resistance were found to have higher levels of omega3fatty acids - and transgenic plants have been created which have increased levels.  So we are in fact eating (and smoking as done originally on tobacco) natural anti-freeze.  Admittedly it's not ethylene glycol, which is nasty stuff to ingest, but it is there. Matthew
imatfaal, Sat, 15th May 2010

Isn't anti-freeze in ice cream and other such products? echochartruse, Fri, 28th May 2010

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